The present invention relates to a novel method of production of tetrakis(pentafluorophenyl)borate derivatives using pentafluorobenzene.
The boron derivative obtainable according to the invention is a very useful substance as an intermediate of a co-catalyst for cationic complex polymerization.
In recent years, scientific literature or patents on studies, in which a cationic complex is generated using tetrakis(pentafluorophenyl)borate derivatives and cyclopentadienyl transition metal complex, so-called metallocene derivatives, and this is used as a catalyst for the polymerization reaction, have increased remarkably. For example, Macromol. Chem. Rapid Commun., A, p.p. 663-667 (1991) etc. are available. However, for the production of tetrakis(pentafluorophenyl)borate derivatives, relatively expensive bromopentafluorobenzene has been used conventionally as a starting substance for the source of pentafluorophenyl group.
In one method bromopentafluorobenzene entered into a bromine-metal exchange reaction using organometallic compounds such as butyllithium to generate pentafluorophenyllithium, which was then reacted with boron trichloride, boron trifluoride, or the like as a starting raw material for the source of boron to synthesize directly. In another method, bromopentafluorobenzene was reacted with magnesium to generate a Grignard reagent such as pentafluorophenylmagnesium bromide, which was then reacted with boron trichloride, boron trifluoride, or the like similarly as a starting raw material for the source of boron to synthesize tris(pentafluorophenyl)borane, and this was further reacted with pentafluorophenyllithium to produce tetrakis(pentafluorophenyl)borate derivatives (J. Organometallic Chem., 2, 245-250 (1964)).
Bromopentafluorobenzene is obtained by brominating pentafluorobenzene. If it is possible to directly produce tetrakis(pentafluorophenyl)borate derivatives from pentafluorobenzene, then the production processes can be reduced by one process, leading to easy availability and also decreased price of a starting raw material. Moreover, literature, in which pentafluorophenyllithium or pentafluorophenylmagnelium bromide is generated using pentafluorobenzene as a starting raw material and this is used for reaction, have already been presented (J. Chem. Soc., 166 (1959), Synthesis of Fluoroorganic Compounds, p141, J. Org. Chem. 29, 2385 (1964) and ibid, 31, 4229 (1966)), but application to the production of tetrakis(pentafluorophenyl)borate derivatives is not made.
In view of the above, the inventors investigated extensively a synthetic method without using relatively expensive bromopentafluorobenzene as a starting raw material by changing the use of bromopentafluorobenzene to that of pentafluorobenzene as a starting substance for the production of tetrakis(pentafluorophenyl)borate derivatives and eliminating the brominating process of pentafluorobenzene, leading to the invention.